The present invention is generally directed to occlusion devices and, more specifically, to intracorporeal occlusion devices which can be used to treat a patent's blood vessels, intracorporeal conduits or other portions of a patient's body. A preferred embodiment can be used to treat intracranial aneurysms, arteriovenous fistulas, and other abnormalities within the cerebral vasculature.
Cerebral aneurysms and other cerebral vascular abnormalities present a significant medical problem to the population of the United States. It is estimated that the number of ruptured intracranial aneurysms yearly is in the tens of thousands, often with devastating consequences for the patient. For a patient who has been diagnosed with a cerebral aneurysm, there are a few treatment modalities currently available. An invasive surgical treatment can be used where access to the external portion of the aneurysm is achieved by placing the patient under general anesthesia, performing a craniotomy, and brain tissue retraction. Once access has been gained to the external surface of the aneurysm, the neck of the aneurysm can be clipped. Clipping the aneurysm neck prevents the ingress of blood into the aneurysm cavity which can lead to rupture. Because of the invasive nature of the procedure and the vulnerability of the brain tissue surrounding the aneurysm, this procedure carries a high degree of risk with concomitant mortality and morbidity rates. This risk is particularly high when the aneurysm has ruptured prior to the surgical intervention.
An alternative to the surgical method currently in use involves percutaneous endovascular intervention. This method generally involves accessing the cerebral aneurysm by means of an intravascular microcatheter which is advanced under flouroscopic imaging over a guidewire or the like within the patient's arteries from a puncture site in the patient's leg or arm. The distal end of the microcatheter is guided over a guidewire within a patient's vasculature and disposed adjacent the neck of the aneurysm. The distal tip of the microcatheter can then be directed into the cavity of the aneurysm and appropriate occlusive devices then delivered from a port in the distal end of the microcatheter. Presently, the most common occlusive device delivered via microcatheter is a vaso-occlusive coil which consists of stainless steel or radiopaque metals such as gold or platinum, tantalum. The vaso-occlusive coils are typically manufactured in a manner similar to the distal coils of a coronary guidewire, having a coil wire material with a small diameter and a coil outer diameter suitable for delivery through a microcatheter. Such vaso-occlusive coils are often given a secondary shape or configuration whereby the coils can be straightened and delivered through the inner lumen of a microcatheter, but form a convoluted or random space filling structure once delivered from the distal end of the microcatheter. The endovascular delivery of vaso-occlusive coils through a microcatheter represents a significant advance in treating cranial aneurysms. However, the coils are hollow bodies, often made of relatively soft metals which are subject to compaction due to the pressure exerted on the deployed coils by the patient's blood flow. Compaction and reforming of the coils leaves them susceptible to dislodging and being displaced within the patient's vasculature, with the potential for causing distal embolization. In addition, compaction of the coils into the dome of the aneurysm or blood clot surrounding the coils can lead to reappearance and regrowth of the aneurysm. Finally, aneurysms with wide necks having a dome to neck dimension ratio of less than 2 to 1 often do not provide a morphology conducive to retention of coils within the aneurysm. Thus currently available coils are generally contraindicated for use in wide neck aneurysms. What has been needed is an intracorporeal space filling device which can be delivered by non-invasive methods, is not subject to compaction or reforming and which is suitable for implantation in wide neck aneurysms.